In many wheel type blow molding machines of the prior art, mechanical hardware, such as cams, are utilized to control various aspects of the blow molding operation, such as the opening and closing of the mold halves. This type of mechanical hardware requires frequent adjustments as these machines are operated to fine tune operation and insure product quality.
Typically, these adjustments are required from the very first machine cycle and thereafter throughout the life of the molding machine to compensate for wearing of the cams, loosening of tolerances and the like. These adjustments, however necessary, require the operator to shut down the blow molding machine. Since these blow molding machines are typically operated continuously, any downtime results in significant financial losses.
For example, U.S. Pat. Nos. 3,310,834, Simpson et al., and 3,764,250, Waterloo, each disclose a plastic blow molding machine including a wheel having a frame supported on a base for rotation about a horizontal axis with a plurality of mold stations mounted on the wheel frame about the rotational axis such that a pair of mold supports for respectively mounting a pair of mold portions move parallel to the rotational axis between open and closed positions of the mold. Such blow molding machines conventionally include a closing station where the mold supports move the mold portions to a closed position to enclose an extruded hot plastic parison within a mold cavity for blowing to the shape of the mold and for subsequent cooling prior to opening at an opening station after approximately 3/4 of a revolution of the wheel.
Also, U.S. Pat. No. 4,698,012, Shelby et al., discloses a multi-station rotary blow molding machine having a plurality of separable blow molds angularly arranged in a serial fashion in a circular array within the machine. Each mold comprises a pair of mold sections, each of which has an internal cavity such that the mold sections, when joined, defining the external configuration of a molded article. The mold sections are mounted in the mold frame for movement toward and away from each other in a direction generally parallel to the axis of the mold frame central shaft and are separately opened and closed as necessary during molding or cleaning operations. The mold sections are opened and closed utilizing a cam arrangement including a cam attached to the stationary support frame, a cam follower associated with each pair of mold sections and carried by the rotary mold frame and a linkage for linking each of the cam followers to its respective mold section.